I'm no lawyer but I can easily see how using the same exact weapons your PD uses could be used against you....

"Look at this guy, he thinks he's a cop. THAT'S why he shot this poor, innocent choir boy, who just happened to have noticed the broken window and was crawling in to alert the homeowner."

I'm pretty sure most anything can be used against used by a prosecutor so-inclined. Your safest bet, in my estimation, would be to use something popular and common among "regular" people. A "normal", unmodified gun. "Normal", commercial ammo.

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Still happily answering to the call-sign Peetza.
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The problem, as you so eloquently put it, is choice.
-The Architect
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He is no fool who gives what he can not keep to gain what he can not lose.
-Jim Eliott, paraphrasing Philip Henry.